The 26-year-old has been with the Pirates for most of pre-season and has now agreed a two-year deal with the club. Manager Mark McGhee has previous experience of Clarkson having worked with him at Motherwell. "I think he is a better player than he has shown, he is certainly a player with more than enough ability to cope with this level," McGhee told the club's official website. "I am expecting him to be a stand out at this division because of where he has come from. "I have got the best out of him before, and I understand him. We are both strikers, and I know what he needs."